Color negative photographic elements are conventionally formed with superimposed red, green and blue recording layer units coated on a support. The red, green and blue recording layer units contain radiation-sensitive silver halide emulsions that form a latent image in response to red, green and blue light, respectively. Additionally, the red recording layer unit contains a cyan dye image-forming coupler, the green recording layer unit contains a magenta dye image-forming coupler, and the blue recording layer unit contains a yellow dye image-forming coupler.
Reproduction of subject images begins with imagewise exposure of color negative elements, commonly referred to as taking elements, in a camera. Following imagewise exposure, the color negative photographic elements are processed in a color developer, which contains a color developing agent that is oxidized while selectively reducing to silver latent image bearing silver halide grains. The oxidized color developing agent then reacts with the dye image-forming coupler in the vicinity of the developed grains to produce a dye image. Cyan (red-absorbing), magenta (green-absorbing) and yellow (blue-absorbing) dye images are formed in the red, green and blue recording layer units respectively. Subsequently the element is bleached (i.e., developed silver is converted back to silver halide) to eliminate neutral density attributable to developed silver and then fixed (i.e., silver halide is removed) to provide stability during subsequent room light handling.
When processing is conducted as noted above, negative dye images are produced. To produce a viewable positive dye image and hence to produce a visual approximation of the hues of the subject photographed, white light is typically passed through the color negative image to expose a second color photographic element having red, green and blue recording layer units as described above, usually coated on a white reflective support. The second element is commonly referred to as a color print element, and the process of exposing the color print clement through the image bearing color negative element is commonly referred to as printing. Processing of the color print element as described above produces a viewable positive image that approximates that of the subject originally photographed.
Whereas color print elements are exposed using a controlled light source, a color negative taking element must function under a variety of lighting conditions. Lighting can range from below the detection threshold of the taking element to very high levels, sometimes in the same subject. When light available during exposure is marginal, increased sensitivity of the color negative elements greatly increases the opportunities for capture of pleasing and superior quality photographic images. When lighting varies widely within the same scene being photographed, wide exposure latitude is required.
Color negative photographic elements that employ a single red recording emulsion layer, a single green recording emulsion layer, and a single red recording emulsion layer are commonly referred to as "single coated". It has been long recognized that increased speed and exposure latitude can be realized in color negative elements by dividing each of the red, green and blue recording layer units into layer units differing in speed. Color negative photographic elements having layer units divided into two or three layer units for recording in the same region of the spectrum arc commonly referred to as "double coated" or "triple coated", respectively. Illustrations of triple coated color negative elements are provided by Chang et al U.S. Pat. Nos. 5,314,793 and 5,360,703 and Kumai et al U.S. Pat. No 3,843,369.
Many corrections for errors in color reproduction are built into color negative elements. For example, if color developing agent oxidized in one layer unit migrates to a second layer unit for creating a dye image of a different hue and reacts with a dye-forming coupler in the second layer unit, color contamination occurs. To prevent this from occurring, it is common practice to incorporate an oxidized developing agent scavenger in an interlayer separating the layer units or, less commonly, in the emulsion layers of the layer units. Oxidized development agent scavenging compounds, also sometimes referred to as anti-stain agents, are illustrated by Research Disclosure, Item 38957, X. Dye image formers and modifiers, D. Hue modifiers/stabilization, paragraph (2). Zengerle et al U.S. Pat. No. 5,585,230 discloses small, similar quantities of a dihydroxybenzene reducing agent applied to all emulsion layers of a triple coated green recording layer unit. Yamakawa et al EP 0 556 700 A1 discloses a ballasted dihydroxybenzene compound in the fastest layer only of a triple coated color negative element. Harder et al U.S. Pat. No. 5,629,140 describes the use of certain hydrazide compounds in color photographic elements in reactive association with 5-pyrazolone magenta dye forming couplers.
Another source of color error in color negative imaging stems from lack of accuracy in color reproduction by dye-forming couplers. Although the error is not large in the taking film, this error is cascaded forward when exposing the color print, resulting in an objectionably large error in color fidelity, absent correction. Typically masking couplers are incorporated in the color negative taking element at concentrations of about 0.2 millimole/m.sup.2 or greater. Illustrations of colored masking couplers are provided by Research Disclosure, Vol. 389, September 1996, Item 38957, XII. Features applicable only to color negative, paragraphs (1) and (2). The colored masking couplers lose or change their color in areas in which grain development occurs to produce a dye image that is a reversal of the unwanted absorption of the image dye. This has the effect of neutralizing unwanted spectral absorption by the image dyes by raising the neutral density of the processed color negative element. However, this is not a practical difficulty, since this is easily offset by increasing exposure levels when exposing the print element through the color negative element.
In recent years increased reliance has also been placed on the incorporation of development inhibitor releasing (DIR) compounds for improving viewable dye images. Development inhibitors, which are rendered mobile by release during color development, improve the dye image by interacting with adjacent layer units to create favorable interimage effects and by sharpening dye image edge definition. Illustrations of development inhibitor releasing compounds are provided by Research Disclosure, Item 38957, cited above, X. Dye image formers and modifiers, C. Image dye modifiers.
Instead of printing through the color negative image in the taking element to produce a viewable color reproduction of the subject photographed, interest has developed in recent years in scanning the image-bearing color negative taking element to create a digital record of the blue, green and red exposure records in the color negative taking element. Since these color records can be manipulated while in electronic form, it has been recognized that many of the image enhancement techniques created for obtaining optimum color reproductions by direct optical printing can be dispensed with while still other image enhancement techniques can be employed for achieving color reproductions using digital color records. Sutton U.S. Pat. No. 5,389,506 illustrates triple coated color negative elements intended to be scanned for image retrieval followed by manipulation of digital color records in electronic form to produce a viewable color reproduction.
Simons UK 2 302 411 describes photographic recording materials that form a silver metal image containing a non-wandering silver halide black-and-white developing agent that may be suitable for color photographic elements intended for scanning. Dye image-forming couplers are absent, and dye images are not formed; the most sensitive layers of color recording units subdivided into more than one layer require the presence of the non-wandering developing agent.